Solutions to the issue of inconsistent installation load and actual applied load on springs

Reply to 1# zhgf86: It seems like the process of selecting a spring in your case is a bit reversed. Normally, one first calculates the installation load, operating load, and displacement, and then selects the spring accordingly. The rate of change in load between the installation load and the operating load is generally required to be no more than 25%. If this difference is too large, it indicates that the spring chosen is not suitable; if the difference is within the acceptable range, it can be adjusted using the spring itself.

It depends on whether your spring is zeroed at operating temperature or at room temperature. When zeroing at operating temperature, the pipeline bears only its own weight under operational conditions, with no additional forces; accordingly, there are additional forces exerted by the spring during installation； Cold zeroing means that the pipeline, in its installed state, bears only its own weight with no additional forces; whereas in operation, there are spring-induced additional forces.

Reply to 2# eddiedong: Then how is your load capacity calculated? Is it based on the elastic coefficient and the working load? If that’s the case, how should the elastic coefficient of the spring be chosen?

Reply to 3# wl0302: It’s like this – I need to provide relevant information to the manufacturer. The software can be used to analyze the working loads and displacements. So, how should I specify the installation loads when providing them to the manufacturer? This involves the issue of elastic coefficients; what value is appropriate for these coefficients?

This post was last edited by macjordan on 2011-6-11 00:33. Reply to 5# zhgf86: I consulted the senior engineers in the team today; the method for selecting springs is thermal zeroing followed by manual reference to tables. We used CAESAR2 for the calculations. First, C2 determines the operating load and the displacement of the spring points. The program automatically selects the appropriate spring based on the spring table you choose (China Power, Sinopec), the operating load, and the displacement values; manually, one has to consult the tables to make such a selection. Once the spring’s stiffness is known, the installation load can be calculated. If the program cannot select a spring from the list, it will automatically choose a constant-force spring (with a stiffness equivalent to zero; as the displacement changes, the force remains constant). For the installation load and operating load, it’s sufficient that the difference is not more than 25%; there is no specific optimal value – it doesn’t matter if it’s a bit higher or lower; the supports specific to that piping system can handle it. Find sample materials from a spring manufacturer; first, select a spring that can withstand the operating load, ideally one whose load capacity falls in the middle of that range. Then determine what the installation load corresponds to at that displacement level. If the load variation is large, choose a spring with lower stiffness (so that the load variation is smaller for the same displacement). Oh, I forgot to mention it – the spring has two markings for identification; one of these markings indicates the load range that each spring can handle, which in turn determines the spring’s strength. A label determines the range of variation in the spring load for the same displacement, that is, the stiffness of the spring.

The method used by the original poster is the one from the example problems on springs in several books: given the operating load and displacement, select the spring and determine the installation load. The installation load obtained in this way is, in my opinion, a theoretical value; it should be compared with the actual installation load. Since the same operating loads and displacements can result in different installation loads depending on the spring stiffness, it is also necessary to ensure that the rate of change of the load does not exceed 25%.

1. There are always errors between any theoretical calculations and the actual installation on site; therefore, the installation load that the pipeline actually bears, as mentioned by the original poster, will differ from the installation load obtained from tables； 2. If the calculations you conduct are accurate and the construction meets the design requirements, generally speaking, the difference between the two will be small, and it will not affect the operation of the pipes ； 3. The installation of springs allows for fine adjustments on-site; it is possible to adjust the springs to their proper position right at the construction site ； 4. The descriptions for the 2nd, 3rd, and 6th floors are incomplete; the installation load is not calculated first. Even in CAESAR’s calculations, the springs that are visible on the surface appear to have installation loads. In reality, the calculation process starts with determining the operating load and displacement; thereafter, the program selects the appropriate spring type, calculates the spring stiffness, and finally determines the installation load ； 5. If the spring model is unknown and it is to be submitted to the manufacturer, only the working load and displacement need to be provided; the spring manufacturer will then determine the spring model, the spring stiffness, as well as the installation load.

Reply to 7# eddiedong: I would like to ask how the actual installation load should be calculated? Hehe

Reply to 5# zhgf86: When calculating, just select \"calculate actual cold\" for the spring

Don’t spring watches like the Caesar have values for the applied load and spring stiffness?